Confusion about when it's my navigation, and when it's ATC

In article ,
Mxsmanic wrote:

If the FMC has a programmed descent in its
route, do I let the FMC start the descent where it sees fit, or do I
force the aircraft to maintain FL290 until ATC explicitly clears me
for my own navigation or for a lower altitude?

It seems what you really want is to read the rules about clearances in
the AIM. The section on the altitude portion of a clearance is 4.4.3.d
and can be found at

http://www.faa.gov/atpubs/AIM/Chap4/aim0404.html


d. Altitude Data.

1. The altitude or flight level instructions in an ATC clearance
normally require that a pilot "MAINTAIN" the altitude or flight level at
which the flight will operate when in controlled airspace. Altitude or
flight level changes while en route should be requested prior to the
time the change is desired.

2. When possible, if the altitude assigned is different from the
altitude requested by the pilot, ATC will inform the pilot when to
expect climb or descent clearance or to request altitude change from
another facility. If this has not been received prior to crossing the
boundary of the ATC facility's area and assignment at a different
altitude is still desired, the pilot should reinitiate the request with
the next facility.

3. The term "cruise" may be used instead of "MAINTAIN" to assign a block
of airspace to a pilot from the minimum IFR altitude up to and including
the altitude specified in the cruise clearance. The pilot may level off
at any intermediate altitude within this block of airspace.
Climb/descent within the block is to be made at the discretion of the
pilot. However, once the pilot starts descent and verbally reports
leaving an altitude in the block, the pilot may not return to that
altitude without additional ATC clearance.

Pixel Dent writes:

3. The term "cruise" may be used instead of "MAINTAIN" to assign a block
of airspace to a pilot from the minimum IFR altitude up to and including
the altitude specified in the cruise clearance. The pilot may level off
at any intermediate altitude within this block of airspace.
Climb/descent within the block is to be made at the discretion of the
pilot. However, once the pilot starts descent and verbally reports
leaving an altitude in the block, the pilot may not return to that
altitude without additional ATC clearance.

I think I read this section before; this paragraph sounds familiar. I
always get instructions to "maintain," though. What's the phraseology
when I get a block of altitudes? Or does it even happen with
frequency in real life? How do I request it (or do I even need to
request it)?

--
Transpose mxsmanic and gmail to reach me by e-mail.

In article ,
Mxsmanic wrote:

Pixel Dent writes:

I think I read this section before; this paragraph sounds familiar. I
always get instructions to "maintain," though. What's the phraseology
when I get a block of altitudes? Or does it even happen with
frequency in real life? How do I request it (or do I even need to
request it)?

In general (i.e. I'm sure someone will come up with an exception), you
won't get things like cruise clearances, VFR on Top Clearances, or block
altitudes unless you specifically ask for them. 99% of the time ATC
gives you an altitude and expects you to stay there until they tell you
otherwise.

That doesn't mean you can't ask for a descent when your FMS tells you it
wants to start down, but there are a number of reasons you may not get
it. There may be conflicting traffic below you or the controlling
authority for the area you are in may have letters of agreement with the
surrounding areas that specify what altitude flights heading in various
directions or to various destinations must be at. In addition sometimes
the controller you're talking to doesn't control the altitude you want
to head down to. For a given ground position there may be three
different controllers handling different altitude blocks and your guy
may not have time to coordinate or even be allowed to descend flights
into the area below you.

Pixel Dent writes:

That doesn't mean you can't ask for a descent when your FMS tells you it
wants to start down, but there are a number of reasons you may not get
it. There may be conflicting traffic below you or the controlling
authority for the area you are in may have letters of agreement with the
surrounding areas that specify what altitude flights heading in various
directions or to various destinations must be at. In addition sometimes
the controller you're talking to doesn't control the altitude you want
to head down to. For a given ground position there may be three
different controllers handling different altitude blocks and your guy
may not have time to coordinate or even be allowed to descend flights
into the area below you.

OK. But this is a bit worrisome in that the FMC apparently already
calculates the optimal descent. If I can't start down in time, I may
not be able to make the other altitudes in the route without holding
or some other diversion to provide more time to descend. For some
reason, the FMC seems to be optimistic about how quickly it can force
the aircraft down. I have to deploy spoilers a lot, and that's even
when the descent starts on time.

Anyway, so I can just say "request descent" when I'm ready to start
down?

--
Transpose mxsmanic and gmail to reach me by e-mail.

In article ,
Mxsmanic wrote:

OK. But this is a bit worrisome in that the FMC apparently already
calculates the optimal descent. If I can't start down in time, I may
not be able to make the other altitudes in the route without holding
or some other diversion to provide more time to descend. For some
reason, the FMC seems to be optimistic about how quickly it can force
the aircraft down. I have to deploy spoilers a lot, and that's even
when the descent starts on time.


Well, I don't fly airliners. I fly a single engine prop that rarely sees
anything above 9000'. That being said I fly a lot of IFR and have never
heard a pilot say "Center, my FMC says I need to start descending now."
Somehow in real life they manage it.

If you're having trouble descending fast enough in the Sim maybe you
just need to slow down the plane to give you more time.

Anyway, so I can just say "request descent" when I'm ready to start
down?

Sure. But even if it's approved that doesn't mean you can just descend
at will to the airport. What you're likely to get is something like
"AB123, descending and maintain one two thousand expect lower in 20
miles."

In general what happens is you gradually get "stepped down" in altitude
via a series of descents as you get closer to the airport until the
final approach controller gets you down to whatever altitude is needed
to start your approach (usually something like 2000' AGL). Once you're
given each new altitude assignment the controller really wants you to
hurry down to the next altitude and level off there so you get out of
the way of other traffic. At times you'll even get requests like "AB123
I need best speed down to one five thousand, I have conflicting
traffic."

To really get a feel of how this all works I'd suggest you go to one of
those live atc sites and listen to an approach controller. You'd be
amazed how much you can learn listening to one for a half hour. At first
it will seem chaotic and then you'll realize there are patterns to what
he's doing with the planes.

Pixel Dent writes:

Well, I don't fly airliners. I fly a single engine prop that rarely sees
anything above 9000'. That being said I fly a lot of IFR and have never
heard a pilot say "Center, my FMC says I need to start descending now."
Somehow in real life they manage it.

I presume they don't say it in so many words, if they say it at all.

Small aircraft seem to be easier to get down towards the ground, or
perhaps they just don't have as far to go. In the Baron that I
prefer, there's no automation of descents, anyway. You can set the AP
to a new altitude and the aircraft will descend to it at your choice
of rates, but it's not fancy like a FMC (nor does it object if you
give it unreasonable objectives).

If you're having trouble descending fast enough in the Sim maybe you
just need to slow down the plane to give you more time.

It's hard to slow the plane down, too. With spoilers deployed on a
737-800, I can descend quickly or slow down quickly ... but not both.

Sure. But even if it's approved that doesn't mean you can just descend
at will to the airport. What you're likely to get is something like
"AB123, descending and maintain one two thousand expect lower in 20
miles."

That would still help me, I think.

In general what happens is you gradually get "stepped down" in altitude
via a series of descents as you get closer to the airport until the
final approach controller gets you down to whatever altitude is needed
to start your approach (usually something like 2000' AGL). Once you're
given each new altitude assignment the controller really wants you to
hurry down to the next altitude and level off there so you get out of
the way of other traffic. At times you'll even get requests like "AB123
I need best speed down to one five thousand, I have conflicting
traffic."

Yes, I've had that. Usually the FMC decides what's best, but at least
I can override that and force a descent at a higher rate (provided
that I can tolerate the airspeed increase).

To really get a feel of how this all works I'd suggest you go to one of
those live atc sites and listen to an approach controller. You'd be
amazed how much you can learn listening to one for a half hour. At first
it will seem chaotic and then you'll realize there are patterns to what
he's doing with the planes.

I have a really hard time just understanding what they are saying
sometimes. I don't know how pilots and controllers manage to
understand each other without making mistakes. Unfortunately, the
same problem exists with virtual flight networks like VATSIM (but for
different reasons).

--
Transpose mxsmanic and gmail to reach me by e-mail.

In article ,
Mxsmanic wrote:

Yes, I've had that. Usually the FMC decides what's best, but at least
I can override that and force a descent at a higher rate (provided
that I can tolerate the airspeed increase).

Well, once again I don't know much about airliners, but in smaller
planes at least you don't generally increase airspeed to descend you
reduce power. At least in the area of the country I fly ATC often has
speed restrictions on the airliners so they couldn't increase speed
during a descent if they wanted to. It's good practice to hold your
airspeed steady while reducing power to make your descent.


To really get a feel of how this all works I'd suggest you go to one of
those live atc sites and listen to an approach controller. You'd be
amazed how much you can learn listening to one for a half hour. At first
it will seem chaotic and then you'll realize there are patterns to what
he's doing with the planes.

I have a really hard time just understanding what they are saying
sometimes. I don't know how pilots and controllers manage to
understand each other without making mistakes.

Practice, practice, practice. Everyone has a hard time understanding at
first but the more you listen the more it makes sense.

Mxsmanic wrote:
I have a really hard time just understanding what they are saying
sometimes. I don't know how pilots and controllers manage to
understand each other without making mistakes. Unfortunately, the
same problem exists with virtual flight networks like VATSIM (but for
different reasons).

If you were in "real" IMC it's even worse (at least until you develop
some practice and learn to keep the picture in your head). Always
seems like ATC is telling you to do something just as you are in the
middle of something else.

Brian

"Mxsmanic" wrote in message
...

Anyway, so I can just say "request descent" when I'm ready to start
down?

Affirm, exactly that. And if you are not going to collide against another
aircraft or terrain, they usually clear you to descend.

Gus Cabre
EGYC

Gus Cabre writes:

Affirm, exactly that. And if you are not going to collide against another
aircraft or terrain, they usually clear you to descend.

I'll try that, then. Is there any difference between "request
descent" and "request lower"? Can I be more specific, like "request
descent to cross BUBBL at 12000" (if the FMC is trying to do that)?

--
Transpose mxsmanic and gmail to reach me by e-mail.